The invention relates to a device for transporting substrates in vacuum coating systems with several stations, substrate holders of an approximately plate-like, flat, parallelpiped configuration which are moved across the stations in a vertical position following a prescribed path of transportation. Pairs of rolling bodies, sliding pads or rollers hold and guide the substrate holders while interacting with guide rails disposed underneath the substrates mounted to the substrate holders.
These substrate holders are either plates with recesses corresponding to the substrates, or frames with cross bars to which the substrates are attached. Generally, the substrate holder serves to hold a plurality of substrates.
A transporting device of the aforesaid kind is known from U.S. Pat. No. 4,042,128 wherein the plate-like substrate holders, with their main plane being in a vertical position, are guided at their upper and lower longitudinal edges between rollers. The rollers can be rotated around vertical axes. At their lower edges the substrate holders rest in addition on support rollers with a horizontal axis of rotation. The lower guiding rollers alone, however, are not able to keep the substrate holders in an exact vertical position and transport them; a stable positioning is only possible with the help of the above guide rollers.
Also known is a transporting device for vacuum coating systems (EP 0 254 145 B1) to which U.S. Pat. No. 4,765,273, corresponds with several stations and a roller system for the guiding and the advance of essentially two-dimensional substrate holders in a vertical position along a prescribed path of transportation across the stations. Pairs of guide rollers are mounted in the area of the lower edge of the substrate holders. These pairs of rollers accommodate the substrate holder between them and rotate about vertical axes. The substrate holders are guided by the roller systems only in the area of their lower edges. The guide rollers have running surfaces which are provided on the lower and upper end of at least one guide roller of one pair of rollers, respectively. The other respective guide roller of the same pair of rollers has at least one moving surface and at least three moving surfaces of one pair of rollers form a stable clamping connection with respect to the substrate holder.
This known transportation device was based on the task of eliminating as far as possible any layer material which is trickling down and could interfere with the coating process.
Further, it is known (DE 31 07 914) to which U.S. Pat. No. 4,544,468 corresponds to thermally pretreat the substrates with a heating device in a separate lock chamber. Finally, it has been proposed to furnish the substrate holder in a transporting device for a vacuum coating system with a foot part which is guided on stationary rails (EP 0 346 815).